This invention relates generally to two-way communication systems and more particularly to trunked radio systems and is more particularly directed towards a method for dynamically regrouping subscriber units.
In a basic trunked system there exists a high degree of flexibility to partition conversations between different groups so that no one agency or district is aware that another agent or district is using this system. Further, these groups can be subdivided into subgroups, so that only those people who need to communicate together on a normal basis are aware when a conversation is in progress. They need not be disturbed by the other subgroups or another agency's communications.
In prior communication systems, a subscriber unit, typically a mobile radio installed in a vehicle, was programmed at the factory to operate within one or more predetermined groups. Accordingly, the radio contained a code plug or programmable read-only memory (PROM) that specified the group, subgroup, and individual ID's enabling a subscriber unit to participate in either individual, subgroup, or group wide calls. If a subscriber unit were programmed to allow communication in more than one group, a selection mechanism, for example a selector switch, is used by the subscriber.
A typical example of such a hierarchy might be to have a group ID consist of a construction company and subgroups assigned to management personnel, delivery personnel, and various on-site teams. Of course, each subscribing unit has its own individual ID for individual calls. Thus, all of management personnel may communicate on a subgroup basis without disturbing the other personnel in the construction company. Also, a group wide call may be made to all individuals associated with a particular company. The same hierarchical analogy can be drawn in the public safety market For example, the groups could be police and fire departments and the subgroups consisting of individual districts.
The communication system described above suffers a significant detriment in that once assigned, the group, subgroup, and individual identities cannot be changed without installing a new code plug in the radio. Typically, this is done in the field at a service center and, of course, once changed cannot be returned to the original ID without another code plug exchange. There exist, however, several situations in which it would be extremely advantageous to dynamically reassign subscriber units to different groups, or create new groups on a permanent or temporary basis. Examples of these situations include tactical operations such as forest fires, airplane crashes, and hostage situations. Also, natural disasters such as flooding, blizzards and tornadoes might be more effectively handled if the subscribing units could be dynamically rearranged to respond to natural or man made emergencies.
Another detriment of the communication system described above is that subscriber units can have selection capability regarding what group calls will be participated in. This is an advantage under normal circumstances where some users have a need to participate in any one of several groups on a normal basis. However, during emergency situations where the radio user's participation in any one particular group is required, the radio may or may not respond to calls in that group, depending on the selection made by the user. The present invention contemplates giving the dispatcher the ability to defeat the selection capability of the subscriber unit, when the subscriber unit is dynamically reprogrammed for an emergency situation, thus ensuring that the subscriber unit responds to calls in the dynamic group.
Some prior art communications systems have attempted to provide a rudimentary multigroup calling by requesting a communication channel for each group to be contacted. However, trunked communications systems operate on the fundamental principle of having few communication channels that are dynamically shared between many groups and subgroups. Accordingly, to make multigroup calls in the fashion of the prior art rapidly consumes most or all of the communication channels Such a system inherently wastes frequency spectrum and may cause other emergency calls to be delayed while the channels are occupied.
The present invention overcomes the detriments of the prior communication systems by dynamically reprogramming or regrouping subscriber units or groups. The present invention contemplates reprogramming one or more subscriber units on an inter or intra-group basis to form a new group that may communicate on a single channel. Once reprogrammed, an individual subscriber may remain in the new group until it is reprogrammed either to its original group or to another group. In another embodiment, entire groups can be combined to form a super group thus providing a rapid, mass restructuring of the subscriber group allocations. The dynamic group regrouping is more typically employed in an emergency situation and is typically somewhat more temporary in nature. Accordingly, provision is made to return to the normal group allocations after a predetermined time period.
Another characteristic of the present invention is that each subscriber unit may still communicate individually in addition to group communications. For example, any subscriber unit may obtain a channel for the purpose of placing a telephone interconnect call. Also, any subscriber unit may obtain a channel for a private conversation with another subscriber unit. When a subscriber unit is dynamically reprogrammed according to the present invention, it still responds to its original ID for individual calls. Thus, the subscriber unit will not miss phone calls, private calls, or "call alerts" initiated by other subscriber units which were unaware of the new dynamic reprogramming ID.
Yet another characteristic of the present invention is the dynamic reprogramming of the "fail-soft" channel. When a trunked system fails, all subscriber units may continue to operate in a mode called fail-soft. In fail-soft, each radio has a programmed channel on which it may continue communications, shared with any other subscriber units which are programmed to the same channel during fail-soft. Obviously, subscriber units which share a common "talk group" should be programmed with the same channel number for fail-soft operation. However, when the present invention dynamically assigns new IDs, the present invention also provides optional dynamic reprogramming of a new fail-soft channel. Thus, dynamically reprogrammed units may continue to communicate on the same channel as other units in the same talk group during fail-soft operation.